As is known in the art, cryogenic infrared detectors are typically made of small band gap (about 0.1-0.2 eV) semiconductors such as HgCdTe (mercury cadmium telluride) grown on a semiconductor substrate, such as a silicon substrate, using molecular beam epitaxy (MBE). In order for proper crystallographic epitaxial growth, the silicon surface upon which the HgCdTe is MBE grown should have a <211> crystallographic orientation. Also, the wafers should have sufficient support thicknesses, typically at least in the order of 100 microns.
As is also known in the art, many imaging application require large arrays of the detectors on a single substrate, or wafer; preferably at least eight inches in diameter. While, eight inch diameter Float Zone (FZ) silicon wafers are readily available, these wafers have surfaces with a <100> crystallographic orientation and are therefore not suitable for MBE formation of the HgCdTe detectors. While silicon wafers produced by the Czochralski (CZ) process produces silicon wafers (CZ silicon wafers) having a surface with a <211> orientation, the CZ silicon wafers having thickness in the order of 100 microns are undesirable in many application because oxygen impurities therein absorb light in many frequency bands where radiation detection is required as in LWIR applications. Further, eight inch diameter CZ silicon wafers with surfaces having a <211> orientation are not readily available.